Moog 3P

 

"A common problem with these synths is their incompatibility with the gate/trig systems used in most other synths. Moog equipment for the most part used a 'high-state' logic called 'S-trig', which maintained a +5V until a trigger was sent, and this was done by dropping the voltage to 0. This is the opposite of what's commonly used in other synths of the time. It also can lead to a problem if a patch used an extensive amount of triggering connections, as each module would cause a voltage drop...and enough of them would send the logic over into low-state and fire the S-trigger. This problem is little-known, and does lead to a good bit of frustration with users who've never worked with Moog gear. But nobody ever said modular synthesis would be easy!"

via vintagesynth.com